Scaling works differently in GUI and from script
It's a context issue and you need to Override the Context

The pivot point is a member of the 3D_VIEW space.  In code below would be area.spaces.active.pivot_point  Example of overriding the context which "fools" the operator into thinking it is being run from the 3D view, not the text editor.

import bpy
context = bpy.context
override = context.copy() # dictionary of context

for area in context.screen.areas:
    if area.type == 'VIEW_3D':
        override["area"] = area
        override["space_data"] = area.spaces.active
        override["region"] = area.regions[-1] # rule of thumb r.type == 'WINDOW'
        break

bpy.ops.transform.resize(override,
                         value=(0.3, 1, 1),
                         constraint_axis=(True, False, False))